A laser diode is an electrically pumped semiconductor laser in which the active medium is formed by a p-n junction of a semiconductor diode similar to that found in a light-emitting diode. A diode laser bar is a device including multiple laser diodes fabricated on a single substrate using semiconductor processing techniques, where the laser diodes are arranged in a straight line separated by small gaps, and light emitted from the laser diode “array” forms a series of linearly arranged parallel beams. Laser diode bars are used in high power laser applications that require more laser light than can be produced by a single laser diode. The most recent generation of high power laser diode bars (e.g., High Power Diode Laser Bar JDL-BAB-50-47-976-TE-120-2.0 produced by Jenoptik) include up to 47 laser diodes per laser diode bar with a 50% fill factor.
Many laser diode applications require the collection and homogenization of the coherent light generated by a laser diode bar. FIG. 10 is a simplified diagram depicting a conventional multiple aperture beam integration optical system 20 that utilizes two microlens arrays and a condenser lens to mix (convert) multiple coherent light beams CL in order to generate a homogenous light illumination pattern LIP on an imaging surface. Although conventional multiple aperture beam integration optical system 20 is suitable for use with laser diode bars having a relatively low number of laser diodes (e.g., 19 laser diodes) and 20% to 30% fill factors, it is difficult to utilize optical system 20 using more recent high power laser diodes (e.g., having 47 laser diodes and 50% fill factors). The microlens arrays of optical system 20 consist of multiple lenslets that are 0.2 mm to 0.5 mm in width and need to be precisely aligned. Higher laser diode bar fill factors (i.e., 40% to 50%) result in the emitter width taking up a larger fraction of the lenslet width, which could cause some of the light to fall on adjacent lenslets in the second microlens array and not be directed by the condenser lens to the proper position on the illumination area. To avoid this problem, additional lens arrays, such as slow-axis collimator telescope (SAC-TEL) microlens arrays, must be used. However, this arrangement requires a large number of individual elements that must be fabricated and precisely aligned, which leads to very high system manufacturing costs.
What is needed is a laser line generator system including an optical system that efficiently and cost-effectively collects and homogenizes coherent (laser) light generated, e.g., by laser diode bars such that the homogenous light forms a line illumination pattern on a target illumination plane. What is also needed is a single-pass imaging system and printing/scanning apparatus that utilize such a laser line generator system.